Freeing stuck oil filler cap.

[JeremyC]

My right side filler cap is firmly seized on to the filler. Not a disaster as the left hand one is free but the cap on the right is rusty and very unsightly so I'd like to replace it at some point.

Does anyone have any thoughts for freeing it. So far it has had several weeks soaking in various penetrating fluids and I've gripped the cap with an oil filter wrench to get leverage but still no joy. I'm reluctant to use heat on a magnesium part for obvious reasons.

Alternatively, does anyone have a spare 4168787 they'd be happy to sell me.

[Argonaut]

Never use heat... you are right. If your car is sitting and is not driven right now then take off the curved part on which the cap sitts in order to allow the fluid to reach to the upper part (upside down possible then). I would use then a piece of wood and a hammer to carefully hit the cap from all sides... then using the fluids again... you might have to repeat this procedure a few times. Using the tool for oil filters is a very good idea.
My 2 cents

[darryl]

I have the same problem and I have tried everything. It will not come off. I am considering cutting it off and buying new caps. They are beat up and look real bad after trying to get them off. Expensive cure.

[beebee246]

Jeremy,
I had a spanner made, and if you remember I offered to send it to you to borrow. My cap was seized solid, and with this spanner it came off in a matter of seconds. If there was sufficient interest I can ask the person who made it for me to make some more. I did notice however that several similar gadgets are available on eBay uk for very little money. Way less than I paid to have my spanner custom made!
Jeremy, call me if you want 07831-290806
Cheers, Brian